Income Taxes (Narrative) (Details) - USD ($) $ in Millions			3 Months Ended	6 Months Ended
	Jan. 01, 2018	Dec. 22, 2017	Mar. 31, 2019	Mar. 31, 2019	Mar. 31, 2018	Sep. 30, 2018
Income Taxes [Abstract]
U.S. Federal statutory income tax rate	21.00%	35.00%
Mandatory repatriation tax payable period				8 years
Repatriation tax liability			$ 66.9	$ 66.9		$ 73.1
Repatriation tax liability due and payable in the next 12 months, may be reduced or offset			5.9	5.9
Tax benefit for reducing deferred tax liability					$ 206.7
Income tax expense for one-time deemed mandatory repatriation					$ 78.2
Provisional tax			$ 0.0	$ 0.0